Conventionally, some electrical junction boxes to be mounted on a motor vehicle include an electrical current sensor that detects an electrical current in a bus bar.
For example, Japanese Patent Public Disclosure No. HEI 9-80080 (JP-A-9-80080) discloses an electrical junction box 1, as shown in FIG. 3. In the electrical junction box 1, a first bus bar 3 is inserted into a through-hole 2a in an electrical current sensor 2. The first bus bar 3 and a second bus bar 4 are secured to a casing 5 by a nut N and a bolt B in a downstream side. The nut N is embedded in a connecting portion 6 in the casing 5. As shown in FIG. 4, the bolt B is inserted through an inner side or an upper side of the casing into bolt holes 3a, 4a in the first and second bus bars 3, 4, respectively, to be fastened by the nut N. After fastening the bolt, a bolt head B1 is disposed in the casing 5.